Semiconductor device including first and second or drain electrodes and manufacturing method thereof

Abstract

An object is to obtain a semiconductor device with improved characteristics by reducing contact resistance of a semiconductor film with electrodes or wirings, and improving coverage of the semiconductor film and the electrodes or wirings. The present invention relates to a semiconductor device including a gate electrode over a substrate, a gate insulating film over the gate electrode, a first source or drain electrode over the gate insulating film, an island-shaped semiconductor film over the first source or drain electrode, and a second source or drain electrode over the island-shaped semiconductor film and the first source or drain electrode. Further, the second source or drain electrode is in contact with the first source or drain electrode, and the island-shaped semiconductor film is sandwiched between the first source or drain electrode and the second source or drain electrode. Moreover, the present invention relates to a manufacturing method of the semiconductor device.

The invention claimed is: 
     
       1. A semiconductor device comprising:
 a gate electrode over a substrate; 
 a gate insulating film over the gate electrode; 
 a first source or drain electrode over the gate insulating film; 
 an island-shaped semiconductor film including a channel forming region over the first source or drain electrode and the gate insulating film; and 
 a second source or drain electrode over the island-shaped semiconductor film and the first source or drain electrode, 
 wherein a part of the second source or drain electrode is formed over and in direct contact with the first source or drain electrode, 
 wherein the island-shaped semiconductor film is sandwiched between the first source or drain electrode and the second source or drain electrode, 
 wherein a thickness of the second source or drain electrode is larger than a thickness of the first source or drain electrode, and 
 wherein the second source or drain electrode covers an edge of the island-shaped semiconductor film. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the island-shaped semiconductor film is one selected from a group consisting of an indium oxide film, an indium phosphorus film and an indium nitride film. 
     
     
       3. The semiconductor device according to  claim 1 , wherein the first source or drain electrode is a titanium film. 
     
     
       4. The semiconductor device according to  claim 1 , wherein the gate electrode and the first source or drain electrode are formed of a same material. 
     
     
       5. The semiconductor device according to  claim 1 , wherein the gate electrode, the first source or drain electrode, and the second source or drain electrode are formed of a same material. 
     
     
       6. A semiconductor device comprising:
 a gate electrode over a substrate; 
 a gate insulating film over the gate electrode; 
 a first source or drain electrode over the gate insulating film; 
 an island-shaped semiconductor film including a channel forming region over the first source or drain electrode and the gate insulating film; 
 an island-shaped impurity semiconductor film comprising an impurity imparting one conductivity type over the island-shaped semiconductor film; and 
 a second source or drain electrode over the island-shaped semiconductor film, the island-shaped impurity semiconductor film, and the first source or drain electrode, 
 wherein a part of the second source or drain electrode is formed over and in direct contact with the first source or drain electrode, 
 wherein the island-shaped semiconductor film and the island-shaped impurity semiconductor film are sandwiched between the first source or drain electrode and the second source or drain electrode, 
 wherein a thickness of the second source or drain electrode is larger than a thickness of the first source or drain electrode, and 
 wherein the second source or drain electrode covers an edge of the island-shaped semiconductor film. 
 
     
     
       7. The semiconductor device according to  claim 6 , wherein the island-shaped semiconductor film is one selected from a group consisting of an indium oxide film, an indium phosphorus film and an indium nitride film. 
     
     
       8. The semiconductor device according to  claim 6 , wherein the first source or drain electrode is a titanium film. 
     
     
       9. The semiconductor device according to  claim 6 , wherein the gate electrode and the first source or drain electrode are formed of a same material. 
     
     
       10. The semiconductor device according to  claim 6 , wherein the gate electrode, the first source or drain electrode, and the second source or drain electrode are formed of a same material. 
     
     
       11. A manufacturing method of a semiconductor device comprising the steps of:
 forming a gate electrode over a substrate; 
 forming a gate insulating film over the gate electrode; 
 forming a first source or drain electrode over the gate insulating film; 
 forming an island-shaped semiconductor film including a channel forming region over the first source or drain electrode and the gate insulating film; and 
 forming a second source or drain electrode over the first source or drain electrode and the island-shaped semiconductor film, 
 wherein a part of the second source or drain electrode is formed over and in direct contact with the first source or drain electrode, 
 wherein the island-shaped semiconductor film is sandwiched between the first source or drain electrode and the second source or drain electrode, 
 wherein a thickness of the second source or drain electrode is larger than a thickness of the first source or drain electrode; and 
 wherein the second source or drain electrode covers an edge of the island-shaped semiconductor film. 
 
     
     
       12. A manufacturing method of a semiconductor device comprising the steps of:
 forming a first conductive film over a substrate; 
 forming a gate electrode using the first conductive film; 
 forming a gate insulating film over the gate electrode; 
 forming a second conductive film over the gate insulating film; 
 forming a first source or drain electrode using the second conductive film; 
 forming a semiconductor film over the first source or drain electrode; 
 forming an island-shaped semiconductor film including a channel forming region by patterning the semiconductor film; 
 forming a third conductive film over the first source or drain electrode and the island-shaped semiconductor film; and 
 forming a second source or drain electrode by patterning the third conductive film, 
 wherein a part of the second source or drain electrode is formed over and in direct contact with the first source or drain electrode, 
 wherein the island-shaped semiconductor film is sandwiched between the first source or drain electrode and the second source or drain electrode, 
 wherein a thickness of the second source or drain electrode is larger than a thickness of the first source or drain electrode, and 
 wherein the second source or drain electrode covers an edge of the island-shaped semiconductor film. 
 
     
     
       13. The manufacturing method of a semiconductor device according to  claim 12 , wherein the first source or drain electrode is a titanium film. 
     
     
       14. The manufacturing method of a semiconductor device according to  claim 12 , wherein the gate electrode and the first source or drain electrode are formed of a same material. 
     
     
       15. The manufacturing method of a semiconductor device according to  claim 12 , wherein the gate electrode, the first source or drain electrode, and the second source or drain electrode are formed of a same material. 
     
     
       16. A manufacturing method of a semiconductor device comprising the steps of:
 forming a gate electrode over a substrate; 
 forming a gate insulating film over the gate electrode; 
 forming a first source or drain electrode over the gate insulating film; 
 forming an island-shaped semiconductor film including a channel forming region over the first source or drain electrode and the gate insulating film; 
 forming an island-shaped impurity semiconductor film added with an impurity imparting one conductivity type over the island-shaped semiconductor film; and 
 forming a second source or drain electrode over the first source or drain electrode, the island-shaped semiconductor film, and the island-shaped impurity semiconductor film, 
 wherein a part of the second source or drain electrode is formed over and in direct contact with the first source or drain electrode, 
 wherein the island-shaped semiconductor film and the island-shaped impurity semiconductor film are sandwiched between the first source or drain electrode and the second source or drain electrode, 
 wherein a thickness of the second source or drain electrode is larger than a thickness of the first source or drain electrode, and 
 wherein the second source or drain electrode covers an edge of the island-shaped semiconductor film. 
 
     
     
       17. The manufacturing method of a semiconductor device according to  claim 16 , wherein the first source or drain electrode is a titanium film. 
     
     
       18. The manufacturing method of a semiconductor device according to  claim 16 , wherein the gate electrode and the first source or drain electrode are formed of a same material. 
     
     
       19. The manufacturing method of a semiconductor device according to  claim 16 , wherein the gate electrode, the first source or drain electrode, and the second source or drain electrode are formed of a same material.